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(11) | EP 2 154 516 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and apparatus for analysing an object |
| (57) A method and apparatus of analyzing a body, wherein a first radiation (X rays) transmitted
through the body and a second radiation (visible, IR and/or ultraviolet radiation)
reflected by the body surface are detected at each point of a series of investigated
points. The data collected for each scanning point are processed so as to maintain
the correspondence between the images obtained using the different techniques.
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Field of the invention
[0001] The present invention relates to an analysis method and apparatus, in particular for valuable objects having a predominantly bi-dimensional development, such as, for example, paintings, boards, doors, cabinet doors, lids, bas-reliefs and the like.
Prior art
[0002] Various systems based on using different types of radiations have been developed in the field of the analysis of objects of various types, in particular works of art. For example, in the field of painting analysis, e.g. for research or restoration purposes, methods based on the reflection of electromagnetic waves (photography), e.g. in the visible, infrared and ultraviolet spectrum, have been developed. Images on photographic film are commonly obtained, although digital photography techniques are also applied.
[0003] Radiographic techniques, i.e. techniques based on radiations capable of crossing the materials to be analyzed, are also used in the field of the analysis of objects such as works of art. X rays are commonly used. Radiographic film may be used for these techniques. A sensor array system may also be provided in order to operate with a digital technique. This type of analysis may also be used for objects, such as those identified above, having a substantially bi-dimensional development. A typical problem related to the above-mentioned types of analysis is the difficulty of having films of the desired size for large objects and, in the case of digital images, of having extended sensor arrays, which besides are very costly, in order to obtain the very high definitions required; moreover, constructing the apparatuses is not simple. The procedure of obtaining a series of partial images, which are then arranged side-by-side to obtain a total image, is often employed. This may occur with great difficulty thus leading to considerable inaccuracies (geometric distortions). Furthermore, it is worth noting that, especially in the case of images obtained with radiations other than visible light, it may be very difficult to associate the individual points of the image with a precise point of the body to be investigated or, similarly, with a point of an image obtained with visible light or even infrared or ultraviolet radiations. The above may restrain the application itself of these techniques, and is however a limit for the information quality which may be obtained.
[0004] Therefore, although analyzing objects is known, above all objects of artistic value, by means of different sources and detectors in the visible, X ray, UV spectrum, etc., the technical problem is to ensure a perfect superimposition of the images and the corresponding information obtained by means of said different technologies, considering that said objects are often large in size and may not be flat.
Summary of the invention
[0005] The problems identified above are solved according to the present invention by a method of analyzing a body, wherein a first electromagnetic radiation crossing the body is detected by a first sensor and a second electromagnetic radiation reflected by the surface of the body is detected by a second sensor at one or more points of a series of points to be investigated, while said first and second sensors integrally move together with respect to the body.
[0006] Where, the term "point" indicates a portion of the body surface analyzed in a certain time by said at least first and second sensors. The size of said portion may be proportionate to the size, type and resolution of the sensors employed. Each of said sensors may have a preponderant acquisition size as compared to the others. According to a first preferred variant, said first and second sensors detect the radiation from the same acquisition point.
[0007] According to a second variant of said method, it may comprise a step of associating the information obtained by said sensors with each point of said series of points, when a same point is scanned by said sensors in different instants, e.g. when said first sensor detects a first radiation from a first point and said second sensor simultaneously detects a second radiation from a second point.
[0008] According to another aspect of the invention, said first and second sensors are adapted to move perpendicularly to a surface of the body to be investigated, the apparatus being adapted to record a focusing distance and to correlate it with the electric signals produced by said first and second sensors.
[0009] According to a preferred variant of the invention, the sensors of the two radiations are integrated in a single sensor sharing the same electric signal processing electronics. According to a preferred aspect, the sensor detections are transformed into digital data in which the detections related to the two radiations associated with a same investigated point remain reciprocally associated. These data may be stored on an appropriate storage medium.
[0010] According to an aspect of the invention, the first radiation are X rays, the second is visible, infrared or ultraviolet light, more preferably visible light. Several radiations may be used simultaneously by increasing the number of sensors and sources so as to combine different image types.
[0011] According to a preferred aspect, these integral movements substantially occur on a plane for scanning the whole body undergoing the analysis, while movements of the sensors or part thereof are possible, especially the sensors related to radiations adapted to be reflected, in a direction normal to the plane, in particular to focus on the surface of the body.
[0012] According to a preferred aspect of the invention, in order to increase the speed of the aforesaid scanning, said adjacent sensors may be developed along a direction perpendicular to a side-by-side direction of the sensors which are sensitive to the various radiations, so as to simultaneously scan several points.
[0014] Simultaneously acquiring several spectrum components according to different wavelengths, possibly with a single mechanical movement, advantageously allows to reduce superimposition (recording) errors of the images obtained, for example, by means of X and visible and/or IR and/or UV radiation.
[0015] Integrating or approaching the sensors related to different electromagnetic radiations as more as possible advantageously allows to eliminate alignment errors and distortions due to the different focusing and/or collimation systems between the various sensors and sources, thus ensuring the simultaneous acquisition of the different electromagnetic sources in relation with a same point of the body.
[0016] It is a particular object of the present invention the content of the appended claims which form an integral part of the present description.
Description of the drawing
[0017] The present invention will now be disclosed by the detailed description of preferred but not exclusive embodiments, provided by way of example only, with the aid of accompanying figure 1, which diagrammatically shows an apparatus according to a preferred aspect of the invention.
Detailed description of an embodiment
[0018] Figure 1 shows an apparatus adapted to analyze a body 1 having a predominantly bi-dimensional development. In the exemplified case, it may be a painting, the apparatus being particularly suitable for analyzing works of art, but it may be any other object, such as a board or a cabinet door, a lid or any other body for which associating an image obtained by reflection of visible light, for example, with an image obtained by a radiographic-type technique is useful. It is apparent that the described technique may be extended to other application fields in addition to those identified above, which are however the preferred fields of application. The apparatus comprises a supporting element 2, which may be rail-shaped, on which a carriage 3, which may be moved by the motor 4, e.g. an electric motor, is movable. Integral with the carriage are rear 5 and front 6 arms, arranged on the two sides with respect to the body 1, which is placed, according to a preferred aspect of the invention, on a plane parallel to the movement direction of carriage 3. Supported by supports moving along the arms, a source 7 of said first radiation, preferably an X ray source, slides on the rear arm 5, and a sensor of said first radiation aligned with the source slides on the front arm 6, so that the radiation beam crosses the body and is picked up by the sensor 8. The source 9, which may be a lamp of appropriate type, and the second radiation sensor 10, which may be mono- or polychrome visible light, infrared, or ultraviolet radiation slide on the front arm 6 integrally with sensor 8. Movement synchronicity ensures the alignment between source 7 and sensor 8. According to needs, apparatuses may be provided in which there is no supporting element and the supports are independently supported and differently synchronized, e.g. for analyzing voluminous bodies which are difficult to be handled. Alternatively, the supports may hang from a supporting element, such as a rail placed above the body to be analyzed. As mentioned, there may be several sources and/or sensors if the use of several types of radiation is intended, in particular different types of radiation adapted to be reflected by the body, e.g. infrared radiation and visible light may be used. According to the present invention, infrared or UV radiation, visible light and X radiation data are simultaneously acquired in a single pass.
[0019] Source 9 may also be omitted if visible light is used and the illumination is sufficient, but having an appropriate light source to illuminate the concerned area is however preferable. The second radiation sensor 10 preferably pointed so as to receive the radiation reflected from the point of the surface of body 1, facing the sensor itself and crossed by the beam of the first radiation, so that the points analyzed with different radiations coincide.
[0020] According to a second variant of the apparatus, the transmitted radiation sensor is expected to pick up the radiation of a first point and the reflected radiation sensor is expected to pick up the radiation of a second point at a known distance from said first point so as to be able to correlate the information concerning a same point as the front arm 6 moves along a scanning direction.
[0021] The sensors of two radiation types (reflected and transmitted) according to the present invention are preferably integrated in a single device in order to obtain the maximum coincidence of the points concerned by the various radiations. The sensors may comprise suitable optical collimation and focusing systems.
[0022] According to a preferred aspect of the invention, the second radiation sensor may move along an axis orthogonal to the plane identified by the movement direction of the sensors and sources as described above, along which the scanning is carried out. This axis is substantially the detection axis of the sensor itself. This allows to focus on the surface at the point to be analyzed, and may simultaneously allow to obtain data related to the distance of the body surface from the sensor.
[0023] The data related to said distances may be stored along with the images so as to obtain more complete information on the shape of the body, in particular when the surface exposed to the sensors is not flat and has protrusions, recesses or undulations. Such a solution is even more advantageous when sources and corresponding sensors of reflected electromagnetic radiations, such as visible light, infrared (IR) or ultraviolet (UV) radiation are simultaneously employed.
[0024] Therefore, according to the present invention, the visible light-sensitive sensor allows to:
- focus on the scanning point for acquiring in the visible field and in the ultraviolet and/or infrared field by means of a movement perpendicular to the surface to be analyzed, with a consequent improved scanning of non-flat bodies,
- for each point, correlate the obtained information on the electromagnetic radiations employed with the focusing distance and thus the shape of the object.
[0025] Other solutions, different from those illustrated, are however possible, e.g. integral sensors oriented parallel to one another. Or sensors in other spectral bands, or reactive to other types of incident signal, such as ultrasounds for example. The distance between the analyzed points is however constant and a processing system of the data picked up by the sensors may compensated for such a difference. Or adjustable sensors and/or pointing systems to allow the correct orientation of the sensors may be provided.
[0026] A computer is preferably part of the apparatus for processing the obtained data and appropriately combine them. Data may be thus stored by said computer.
[0027] The computer may control, even by means of appropriate software, the synchronized movement of source and sensors by wired systems or even remote control systems.
[0028] An embodiment is shown by way of example, in which the transmitted radiation sensor is placed on the same side as the sensor and source of the second radiation, which may be a radiation in the visible or IR or UV spectrum, while the first radiation source is on the opposite side. If deemed appropriate, the position of the source and first radiation sensor may be exchanged, since the first radiation is intended to cross the body being investigated.
[0029] The apparatus may be constructed in other manners than that shown. For example, telescopic or articulated arms, which form the front and rear movable supports, may be used providing that the alignment between source and sensor is ensured, by virtue of the integral or anyway synchronous movement. Embodiments, such as the one shown, which permit to scan according to orthogonal axes and allow to immediately store the points of the image in a matrix in which said points are associated with Cartesian coordinates, are particularly useful. The apparatus may comprise supporting devices for positioning and withholding the body to be analyzed in the appropriate position.
[0031] Photodiodes, phototransistors or photomultipliers may be used for visible light. For the infrared spectrum, an example are InGaAs or Ge sensors; for example, an array of eight sensors of this type has been deemed adequate.
[0032] The visible light sensor may be monolithically integrated on CMOS chips along with the reading circuits (thus made of silicon) and may be provided for grayscale viewing or RGB components of light may be distinguished by means of color filters.
[0033] The X ray sensor may be made of silicon, often high resistivity silicon. The array thus obtained may be, as the infrared sensor, connected by means of bump-bonding or wire-bonding at the opposite free side of the CMOS chip. The chip - pixel-to-pixel sensor assembly allows to make a complex electronic component capable of discriminating the energy and the statistic of the detected photons, thus providing a further spectrum resolution within the X band for the obtained data, for each single acquisition and each observed point. Discriminating various energies indeed allows to recognize different materials within the investigated body.
[0034] According to a preferred variant of the invention, the use of at least one multi-spectrum sensor is preferred, i.e. a sensor capable of simultaneously detecting electromagnetic radiations, such as visible light, infrared radiation and X rays. Although monolithic integrated sensors adapted to detect radiations in the visible and infrared spectrums by means of CMOS technology are known, an integrated sensor adapted to detect visible light, infrared and X radiations form an integral part of the present invention.
[0035] The use of materials such as high resistivity silicon is preferred for making the multi-spectrum sensor, with a thickness in the sensitive region of the order of hundreds of micrometers, or however at least a size order thicker than the sensitive region which is used in typical microelectronic processes (a few micrometers), or gallium arsenide, cadmium telluride or other composite semiconductors.
[0036] With the electronic processing part thereof, the CMOS sensor, in addition to being sensitive to visible radiation, is able to process the signals received from IR and X sensors.
[0037] According to a first variant of the sensor, a first part sensitive to the IR radiation is attached to a CMOS sensor, while an X radiation sensor is placed close to the CMOS and connected by wire-bonding to the processing electronics thereof.
[0038] The connection between the IR sensor and the CMOS and between the X ray sensor and the CMOS may be made by wire bonding or bump bonding.
[0039] According to a further variant, the CMOS and IR sensors are made in a single body using a single electronic processing section as shown above.
[0040] By using a standard CMOS, a single output channel proportional to the total detected light intensity may advantageously be obtained, while 3 or 4 channels need to be processed if imaging sensors with color filters are used. In both cases, there is one extra channel dedicated to the IR sensor signals.
[0041] According to the present invention, arrays of 3xN sensors of the above-mentioned three types or multiples thereof may be used.
[0042] The X radiation sensor may comprise collimation systems so as not to require a specific focusing as compared to that made for the visible and/or infrared and/or ultraviolet radiation.
[0043] The radiation source may consist of one or more tubes so as to increase the spectral content of the emission. Normally, the tubes may be monochromatic (they emit at a certain energy) but also have secondary emission peaks: these may be exploited for an energy analysis as mentioned above.
[0044] The X ray tubes may have collimation systems capable of obtaining a radiation beam which does not require any further focusing. For example, the result may be obtained by means of a metal shielding appropriately dimensioned according to the geometric features of the system.
[0045] If deemed appropriate, the various sensors may be provided with filtering means to improve sensitivity of the single bands.
[0046] The described technique is particularly useful because it allows to associate the images obtained with various techniques in a point-by-point fashion, so as to have a precise reference for the images, e.g. radiographic images, with respect to the body image obtained with visible radiation; this obviously also applies to other techniques, such as the infrared or ultraviolet techniques, providing very accurate information.
[0047] A further resulting advantage is indeed the possibility of operating with single sensors or arrays with a small number of sensors for a complete analysis. Longer scanning times are certainly acceptable in the field of application of analyses on unanimated objects and are widely compensated by the aforesaid advantages.
1. A method of analyzing a body, wherein a first electromagnetic radiation crossing the
body is detected by a first sensor (8) and a second electromagnetic radiation reflected
by the body is detected by a second sensor (10) at one or more points of a series
of points to be investigated, while said first and second sensors integrally move
together with respect to the body.
2. A method according to claim 1, wherein said first and second radiations are simultaneously
detected; said first and second sensors detecting electromagnetic radiations either
from a same point or from points located at a known distance.
3. A method according to claim 2, wherein said simultaneous detection is obtained by
means of a single sensor which is sensitive to both radiations.
4. A method according to claim 1, further comprising a step of associating the information
obtained from said sensors with each point of said series of points when a same point
is scanned by said sensors at different instants.
5. A method according to any one of the preceding claims, wherein said first radiation
are X rays and said second radiation is visible and/or infrared and/or ultraviolet
light.
6. A method according to claim 5, wherein at least two radiations adapted to be reflected
are used.
7. A method according to claim 5, wherein a body focusing distance is in relation with
the detection of at least said first and second electromagnetic radiations for characterizing
non-flat bodies.
8. A method according to claim 6, wherein a focusing distance is in relation with said
at least two electromagnetic radiations adapted to be reflected and/or with said first
electromagnetic radiation.
9. A method according to any one of the preceding claims, wherein the analysis comprises
scanning a series of points in sequence, preferably covering all the points of at
least one portion of a body surface.
10. An apparatus for analyzing a body (1), comprising a first sensor (8) of a first radiation
crossing the body, a second sensor (10) of a second radiation reflected by the body
characterized in that said first and second sensors are integral with each other and adapted to recapture
the body to be investigated.
11. An apparatus according to claim 10, wherein said first (8) and second (10) sensors
are adapted to move perpendicularly to a surface of the body to be investigated; the
apparatus being adapted to record a focusing distance and correlate it with the electric
signals produced by said first and second sensors.
12. An apparatus according to claim 11, wherein said first sensor is adapted to detect
an electromagnetic X radiation and said second sensor is adapted to detect a visible
and/or IR or UV radiation.
13. An apparatus according to claim 12, wherein said first and second sensors are integrated
in a single sensor wherein an IR radiation-sensitive layer and a visible radiation-sensitive
layer share the same electric signal processing electronics.
14. An apparatus according to claim 12, comprising a movable front support (6) and a movable
rear support (5), adapted to synchronously move together and to be placed on two opposite
sides of the body to be investigated and comprising an X electromagnetic radiation
source (7) placed on one of said supports and said first sensor (8) being placed on
the other of said supports.
15. An apparatus according to claim 14, comprising a movable front support (6) and a movable
rear support (5), adapted to synchronously move together and to be placed on two opposite
sides of the body to be investigated and comprising an X electromagnetic radiation
source (7) placed on a first of said supports and said first sensor (8) being placed
a second of said supports and comprising a source of visible and/or IR or UV radiation
on said second of said supports.